Summary of Significant Accounting Policies - Fair Value Hierarchy for Financial Assets (Detail) (Recurring [Member], USD $) In Thousands, unless otherwise specified	Jun. 29, 2013	Dec. 29, 2012
Fair value hierarchy for financial assets
Total	$ 36,797	$ 33,622
U.S. Treasuries [Member]
Fair value hierarchy for financial assets
Total	34,999	31,999
Money Market funds [Member]
Fair value hierarchy for financial assets
Total	1,798	1,623
Level 1 [Member]
Fair value hierarchy for financial assets
Total	36,797	33,622
Level 1 [Member] | U.S. Treasuries [Member]
Fair value hierarchy for financial assets
Total	34,999	31,999
Level 1 [Member] | Money Market funds [Member]
Fair value hierarchy for financial assets
Total	1,798	1,623
Level 2 [Member]
Fair value hierarchy for financial assets
Total
Level 2 [Member] | U.S. Treasuries [Member]
Fair value hierarchy for financial assets
Total
Level 2 [Member] | Money Market funds [Member]
Fair value hierarchy for financial assets
Total
Level 3 [Member]
Fair value hierarchy for financial assets
Total
Level 3 [Member] | U.S. Treasuries [Member]
Fair value hierarchy for financial assets
Total
Level 3 [Member] | Money Market funds [Member]
Fair value hierarchy for financial assets
Total